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Braking on IS350

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Old Jul 18, 2007 | 03:36 PM
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Default Braking on IS350

Guys is this normal for the brakes to make a jeking motion when i apply the brake light. When ever im driving and im going around 40-50 Mph and when i apply the brake i feel a jerking motion then i feel the gears going down then ill feel another softer jerk. IS this normal or are the brkaes supposed to do this since its a sports car. Im not annoyed by it but i actually like the jerk but yet again is something that i should get checked out??
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Old Jul 18, 2007 | 03:42 PM
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The jerking is the engine braking caused by the ECU adapting to your driving style. It does this by keeping the transmission in a lower gear, just in case you have the need to brake, then instantly accelerate.
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Old Jul 18, 2007 | 03:43 PM
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Originally Posted by Irishfan
The jerking is the engine braking caused by the ECU adapting to your driving style. It does this by keeping the transmission in a lower gear, just in case you have the need to brake, then instantly accelerate.
oh ok, thats cool. thanks for the quick info
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Old Jul 18, 2007 | 04:27 PM
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Originally Posted by Irishfan
The jerking is the engine braking caused by the ECU adapting to your driving style. It does this by keeping the transmission in a lower gear, just in case you have the need to brake, then instantly accelerate.
Noticed this too and wandered about the cause. Thanks for the info. CL comes thu again.
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Old Jul 18, 2007 | 04:38 PM
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If there is nothing wrong within your front end, bearings, and brake system... you prolly just need those front rotors to be re-surfaced (if thickness stands within spec), it will be $100 more or less...

If this problem is on going for a while already, you prolly need to change pads and rotors... that will be... $500 +/- maybe with oe parts.
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Old Jul 18, 2007 | 06:23 PM
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This may not be what youre refering to but the car also has the brake assist. I sometimes find myself trying to brake gently and the brake assist progressively starts applying more braking, sometimes more than i want. I've kind of gotten used to it now, the hard part is going back to my other car that doesnt have it.
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Old Jul 19, 2007 | 02:40 PM
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Originally Posted by yogi350
This may not be what youre refering to but the car also has the brake assist. I sometimes find myself trying to brake gently and the brake assist progressively starts applying more braking, sometimes more than i want. I've kind of gotten used to it now, the hard part is going back to my other car that doesnt have it.
Well actually now this makes more sense. I didnt know it did that untill now. I came from a SUV a 05 Dodge Durango so it feels wierd when i apply little amout of brake while going at 40-50 MPH then the brake assist kicks in, But i like it, "Its Ver Nice" (Borat)
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Old Jul 19, 2007 | 03:55 PM
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It's not brake assist. Brake assist kicks in only during a panic stop, and applies the brakes full force. Here is a description of the system from Lexus: http://www.lexus-europe.com/technolo..._IS_250#active

If you keep your center display in the "current gear" indicator mode, you'll see that the "jerks" you feel are not the brakes at all, but actually the car downshifting.

Last edited by Bichon; Jul 19, 2007 at 03:59 PM.
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Old Jul 19, 2007 | 04:40 PM
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Originally Posted by Bigrahizzl
Guys is this normal for the brakes to make a jeking motion when i apply the brake light. When ever im driving and im going around 40-50 Mph and when i apply the brake i feel a jerking motion then i feel the gears going down then ill feel another softer jerk. IS this normal or are the brkaes supposed to do this since its a sports car. Im not annoyed by it but i actually like the jerk but yet again is something that i should get checked out??
Like most have said, "you're normal." Mine does it also.

Cheers,
Old Oiler
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Old Jul 19, 2007 | 04:52 PM
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If your car is in power mode the downshifts are much more noticeable when braking.
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Old Jul 19, 2007 | 05:24 PM
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Originally Posted by davidbenji
If your car is in power mode the downshifts are much more noticeable when braking.
Yep... PWR mode pretty much applies a downshift even if you bearly press the break pedal.
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